We report an in-situ, non-invasive approach to quantify oxygen partial pressure
in microfluidic lab-on-a-chip (LoC) devices. LoC systems provide a versatile
platform to culture biological systems. As they allow a detailed control over
the growth conditions, LoC devices are finding increasing applications in the
culture of cells, tissues and other biological systems . Integrated
microfluidic NMR spectroscopy  allows non-invasive monitoring of metabolic
processes in such systems. Quantification of oxygen partial pressure would help
ensuring stable growth conditions, and provide a convenient means to
assess the viability of the cultured system. However, oxygen, one of the most
important metabolites, cannot be quantified using either proton or carbon NMR
As is well known, the oxygen partial pressure can be determined by MRI in vivo
by measuring the 19F spin-lattice relaxation time of perfluorinated agents .
Here, we show that the oxygen partial pressure in microfludic devices of 2.5 µl
can be quantified using the 19F spin-lattice relaxation rate of perfluorinated
tributylamine. The compound is added to the aquous perfusion
medium in the form of micrometer-sized droplets. Our set up comprises a
microfluidic device and a PDMS layer sandwiched between two 3D printed holders.
The droplet emulsion is delivered via a syringe pump and carbogen is delivered
through a separate channel. The semi- permeable PDMS layer acts as a diffusion
bridge between the liquid and gas channels, allowing for oxygen to diffuse into
the emulsion. T1 is obtained through standard inversion recovery experiments
detected using a home-built transmission-line probe. Due to the non-toxic nature of droplet emulsion, it can be easily incorporated into the perfusion fluid
allowing for quantification of tissue oxygen levels.
1. Gracz et al., Nature Cell Biology 17, 340–349, 2015
2. M.Sharma, M.Utz, J.Mag.Res 303, 75-81, 2019.
3. R.Manson et al., Magnetic Resonance in Medicine 18, 71-79, 1991.